1. Field of the Invention
This invention relates to an offshore platform for producing oil from a well drilled to an underground hydrocarbon reservoir beneath the body of the water in which the platform is located. It relates especially to a structure for protecting the wellhead from damage due to fire. The term "wellhead", as used herein, includes the "Christmas tree", which also includes the master valves, tees, swab valves, and wing valves, which sit on the casing spool and hanging equipment. It concerns particularly the placing of the wellhead beneath the surface of the body of water and includes a shield to protect the wellhead from any falling debris.
2. Setting of the Invention
In recent years, there has been considerable attention directed to the drilling and production of oil and gas wells located in water. Walls may be drilled in the ocean floor from either fixed platforms in relatively shallow water, or from floating structures or vessels in deeper water. At present, the most widely used means is the fixed platform which includes the driving or otherwise anchoring of long piles in the ocean floor. Such piles extend above the surface of the water with a working deck or platform attached to the top of the piles. In using such fixed platforms, the drilling rig is set on the platform above the surface of the water and the wells are normally drilled using generally dry land techniques. After the well is drilled, producing equipment, separators, wellheads, and the like, are located on the platform itself above the surface of the water. There are usually many wells, e.g., eight to 16, drilled from one offshore platform, and this involves a corresponding number of wellheads. One problem with this particular type setup is the danger of damage to the wellheads by fire. There has been at least one instance that a fire occurred and the wellheads worked perfectly in shutting off the flow of fluid, but excessive heat from the burning of petroleum being processed, or fuel stored on the deck of the platform itself, damaged the wellheads so they leaked. That fire would have burned itself out as soon as stored fuel or petroleum on the platform was exhausted except for the fact that the fire and heat damaged the wellheads causing them to leak and add more fuel to the fire. This, of course, resulted in the wells producing in an uncontrolled state and the fire continued for weeks until such time as the wells were killed by drilling directional wells for bottom-hole control. This is a tremendous loss of matural resources, and also a tremendous expense. Presently, there is a reluctance in the offshore industry to include normal production equipment on the same platform structure with the producing wellheads. This reluctance is based on safety considerations, primarily to prevent exposing the producing wellheads to fire or high temperature resulting from fire. As an alternative, therefore, the industry is often setting two platforms side-by-side with the wells on one platform and the production equipment on the other. Needless to say, this is a significant added investment over a single platform installation.
3. Prior Art
No prior art is known which describes the invention claimed herein. There is considerable art in the field of offshore producing platforms. Some related art, dealing with installing controls and operating underwater wellheads, include U.S. Pat. Nos. 2,970,646; and 3,395,755; and Canadian patent No. 890,146. All of these patents are concerned with an undersea well where the wellhead controls are on the sea floor.